class Zuhe{
public static void main(String args[]) {

   int temp[]=new int [args.length];
   int sum;
   for(int i=0;i<args.length;i++) {
        temp[i] = Integer.parseInt(args[i]);
   }
   sum=fact(temp[0],temp[1]);
   if(sum == 0)
    System.out.println("error");
    else
     System.out.println(sum);
}
}
